pQueue-MAC: An Energy Efficient Hybrid MAC Protocol for Event-Driven Sensor Networks

Although a lot of MAC protocols have been proposed to deal with burst traffic in wireless sensor networks, most of them do not optimize the energy efficiency of low and nonperiodic traffic, which actually wastes a lot of energy. To solve the problem, we propose a novel MAC protocol, called pQueue-MAC, to achieve high energy efficiency when no event is detected and still guarantee immediate yet energy efficient data transmission when events are detected. pQueue-MAC uses preamble sampling to check potential communications in low traffic condition. Specifically, through short channel listening, nodes can decide whether there is data destined for them, based on which nodes choose to sleep for energy conservation or keep active for data exchange. Moreover, adaptive channel listening scheme is adopted for dynamic traffic load. When load increases, based on the load information collected from son nodes by piggybacking, cluster heads adaptively allocate TDMA slots and embed the new schedule information into the beacon frame broadcasted to son nodes. We have implemented pQueue-MAC on STM32W108 chips that offer IEEE 802.1.5.4 standard communication and conducted extensive experiments to evaluate its performance. Experimental results show that pQueue-MAC outperforms other typical MAC protocols in hybrid traffic load situation, since it achieves higher energy efficiency and lower transmission latency.